The testing is non-invasive: it involves taking a blood sample from the mother. The pregnancy is not put at risk of miscarriage, or from other adverse outcomes that are associated with invasive testing procedures such as amniocentesis.

NIPT provides fewer false-positive and false-negative results than combined first trimester screening for trisomy 21, 18 and 13.

It is important to note that NIPT is a screening test and does not provide a definitive genetic diagnosis, as NIPT cannot differentiate potential chromosome differences between the placenta and fetus. A definitive genetic diagnosis of the fetus requires cytogenetic analysis of either amniotic fluid or chorionic villus sampling (CVS).

* Proportion fetuses with trisomy correctly identified by the test as high probability of disorder.

# Proportion of normal fetuses incorrectly identified by the test as high probability of disorder.

NIPT Performance data in a general screening population

NIPT can be ordered by healthcare professionals for women with pregnancies of at least 10 weeks’ gestational age. This test can be requested for any singleton or twin pregnancy, including those conceived naturally or by IVF using the patient’s own egg or a donor egg.

Note that, in twin pregnancies, sex chromosome (X and Y) analysis can determine fetal sex but not sex chromosome conditions. This test is not suitable in the case of a vanishing twin. The sex of twins will be reported as one result. If male, one or both of the twins will be male. If female, both twins will be female.

The test does not assess risk for mosaicism, partial trisomies or translocations.

There needs to be enough fetal DNA in the maternal blood to be able to provide a result. If there is insufficient fetal DNA in the sample (which occurs in 2% of cases), another blood sample from the mother may be required. This will be processed in the laboratory at no extra charge.

The NIPT consists of a scan and a blood test. The scan is required to accurately date the pregnancy and to ensure the pregnancy is progressing normally. The scan is mandatory as part of the NIPT screening and should be performed within 24/48 hours of having the bloods taken.

If after the scan, the baby is measuring less than what you thought by your dates, you will be asked to return for a further visit. The blood test needs to be performed after 10 weeks and 2 days, so as there is enough of the baby’s DNA in your blood circulation. We will need to repeat the scan and the cost is €90.

The mother’s sample and completed request form need to be sent to TDL Genetics, where the test is performed on the DNA extracted from her blood sample.

NIPT does not provide information on mosaicism, partial trisomies or translocations, or other rare chromosomal abnormalities. If the ultrasound scan shows a high nuchal translucency or other major physical defects such as brain abnormalities, heart abnormalities, the risk for some rare chromosomal defects may be high. In such cases, the mother may choose to have a CVS or an amniocentesis.

The non-invasive prenatal test does not provide information on other physical defects such as spina bifida, or information on fetal growth. It is therefore advisable that the mother has all the usual ultrasound scans during her pregnancy.

Trisomy 21 is the most common trisomy, at the time of birth. Also called Down syndrome, it is associated with moderate to severe intellectual disabilities and may also lead to digestive disease, congenital heart defects and other malformations.

Trisomy 18 (Edwards syndrome) and Trisomy 13 (Patau syndrome) are associated with a high rate of miscarriage. These babies are born with severe brain abnormalities and often have congenital heart defects as well as other birth defects. Most affected individuals die before or soon after birth, and very few survive beyond the first year of life.

The X and Y chromosomes typically determine biological sex. Sex chromosome aneuploidies occur when there is a missing or extra copy of one of these chromosomes.

The TDL NIPT with the optional sex chromosome aneuploidy panel can assess risk for XXX, XYY, XXY (Klinefelter syndrome), and monosomy X (Turner syndrome). This panel is only performed if specifically requested.

If you’re interested, please discuss whether it’s appropriate for you with your healthcare provider.

On rare occasions, NIPT is unable to provide an assessment of the probability of specific chromosome disorders. This usually reflects the complex biology of genetics and pregnancy, and is not due to a failure in the laboratory.

If the NIPT cannot provide a specific assessment, it is not worth repeating, unless advised by the laboratory. A decision about other tests (maternal serum screening, detailed ultrasound, amniocentesis or CVS) should be based on the doctor’s assessment of all risk factors identified, and may require specialist consultation.

Most reports are available within a few working days. We’ll confirm the current turnaround at booking and contact you as soon as your result is ready.

The results will be sent to you via an encrypted email.

We’ll invite you back for a repeat blood draw at no extra charge. If a further sample still can’t be reported, we’ll discuss alternatives and next steps.

Yes. NIPT does not check your baby’s anatomy, growth, or placental position. Please continue with all recommended ultrasound appointments.

Yes, Non-Invasive Prenatal Testing (NIPT) is generally suitable for pregnancies involving twins, IVF, and donor eggs, with some important considerations.

NIPT can be ordered by healthcare professionals for women with pregnancies of at least 10 weeks’ gestational age. This test can be requested for any singleton or twin pregnancy, including those conceived naturally or by IVF using the patient’s own egg or a donor egg.

Note that, in twin pregnancies, sex chromosome (X and Y) analysis can determine fetal sex but not sex chromosome conditions. This test is not suitable in the case of a vanishing twin. The sex of twins will be reported as one result. If male, one or both of the twins will be male. If female, both twins will be female.

The test does not assess risk for mosaicism, partial trisomies or translocations.

Yes. The Doctors Laboratory requires a special request form to ensure that they obtain the required information to interpret the analytical result correctly.

In approximately 1:2,000 pregnancies, the cells of the outer placenta (the cytotrophoblast) have an abnormal number of chromosomes compared to the developing fetus. This can potentially cause a false positive, i.e., NIPT identifies a chromosome abnormality in the placental DNA circulating in the mother’s plasma, but the baby turns out to be fine. For this reason, a NIPT result that indicates a high probability of a chromosome disorder must be confirmed by invasive genetic testing before making any major decision about the pregnancy.

Conversely, in up to 1% of fetuses with a major chromosome disorder, the placental chromosomes may be normal. NIPT may report that there is no evidence of a chromosome disorder while the developing fetus actually has a chromosome disorder, i.e. a false negative result. For this reason, a “low risk” NIPT result that is at variance with firm evidence of a fetal problem, e.g. malformation evident on ultrasound, must be reviewed and invasive genetic testing considered.

In approximately 1:2,000 pregnancies, the cells of the outer placenta (the cytotrophoblast) have an abnormal number of chromosomes compared to the developing fetus. This can potentially cause a false positive i.e. NIPT identifies a chromosome abnormality in the placental DNA circulating in the mother’s plasma but the baby turns out to be fine. For this reason, a NIPT result that indicates a high probability of a chromosome disorder must be confirmed by invasive genetic testing before making any major decision about the pregnancy.

Conversely, in up to 1% of fetuses with a major chromosome disorder, the placental chromosomes may be normal. NIPT may report that there is no evidence of a chromosome disorder while the developing fetus actually has a chromosome disorder i.e. a false negative result. For this reason, a “low risk” NIPT result that is at variance with firm evidence of a fetal problem e.g. malformation evident on ultrasound, must be reviewed and invasive genetic testing considered.

NIPT may be done at any time after the 10th completed week of pregnancy. However, the usefulness of information obtained after 20 weeks may be limited by other factors, such as the interventions available at later gestations. NIPT has not been validated at gestational ages less than 10 completed weeks. There may be insufficient fetal DNA present in the maternal plasma to provide a reliable result, and samples under 10 weeks will not be accepted for testing.

No.

NIPT examines DNA fragments from the fetus and placenta that are circulating in the mother’s blood. These DNA fragments last only an hour or so, and are replaced continuously from the placenta throughout the pregnancy. Once the baby has been born, the remaining fragments of the baby’s DNA disappear from the mother’s circulation within a couple of hours.

As a result, there are no remaining DNA fragments from the baby that might interfere with NIPT in a subsequent pregnancy.

NIPT is not recommended if the fetus is known to have major congenital malformations.

Malformations could be caused by a variety of chromosome disorders or be non-chromosomal in origin. NIPT provides an assessment for selected chromosome disorders, and in this setting the underlying disorder may be missed by NIPT. The more appropriate genetic investigation may be invasive testing by CVS or amniocentesis with fetal chromosome studies by microarray.

No.

If the event of fetal demise, fetal DNA can continue to be detected in the maternal circulation for weeks or even months while the placenta remains in situ. NIPT cannot determine whether the fetal DNA has come from a viable or non-viable fetus.

In the event of a demised twin (or “vanishing twin”), the fetal DNA from that twin may compromise the accuracy of NIPT of the surviving twin. Our NIPT has not been validated in the presence of a demised twin, and NIPT is not able to be performed if there is known to be a demised twin at the time of sample collection.

The decision about which date is more likely to be correct must be resolved by the doctor responsible for managing the pregnancy. NIPT does not provide any information regarding gestation.

It may be preferable to defer collecting a blood sample for NIPT until a gestation of 10 completed weeks as determined by the later date. In other words, it is usually preferable to err on the side of taking a sample for NIPT later rather than earlier in the pregnancy.

The NIPT assay assumes that the mother has normal chromosomes and normal amounts of DNA in her blood. The accuracy of NIPT could be compromised by any maternal condition which fails to meet these assumptions e.g. triple X syndrome, mosaic chromosome disorder, cancer, recent blood transfusion, and bone marrow or organ transplantation. NIPT is not able to be performed in such settings.

There is an inverse relationship between maternal body weight and the concentration of fetal DNA (fetal fraction) in maternal plasma. With increasing body weight, there is an increasing probability that there will be insufficient fetal DNA to provide a reliable result. There is no maternal weight threshold at which we do not recommend NIPT. A woman who weighs 140 kg will, on average, have a fetal fraction that is approximately half that of a woman weighing 70 kg.

This relationship between maternal weight and fetal DNA does not compromise the accuracy of NIPT as we confirm that there is sufficient fetal DNA to produce a reliable result in every maternal blood sample tested. However, this relationship does increase the possibility that we cannot provide a result because there is insufficient fetal DNA.

We do not recommend NIPT as a method of screening for cancer.

There have been reports of some women having strikingly abnormal NIPT results that seem to be incorrect, i.e. the fetal chromosomes are normal when checked. Some of these women have subsequently been found to have cancer. The abnormal NIPT result reflected abnormal DNA from the cancer in the mother’s circulation rather than abnormal DNA from the fetus.

These are rare events (a handful of instances among millions of women tested). The reliability of NIPT in detecting cancer during pregnancy is not known. We do not recommend NIPT as a method of screening for cancer.

The NIPT assays used by TDL are designed to provide a very clear indication regarding the probability of the developing fetus having, or not having, a specific chromosome disorder. In more than 99% of women tested, we are able to provide a very clear indication either way.

However, in a small number of instances, we may be unable to provide an assessment for all conditions considered in the test, or for only some conditions.

There are various reasons why NIPT cannot provide a clear answer for one or more of the questions being asked by the requesting doctor:

• There may be insufficient fetal DNA present for an assessment about a specific disorder. Some conditions may be harder to resolve than others.
• There may be uncommon harmless variations in the DNA from either mother or fetus that interfere with the assessment for a given disorder.
• The placenta may have a mixture of normal and abnormal DNA that differs from that of the fetus, making it impossible to provide a confident answer regarding a specific disorder.